Serial serum MCA measurements in the follow-up of breast cancer patients.

Mucin-like carcinoma-associated antigen (MCA) was serially assayed in 58 women with histologically proven breast cancer after their treatment for primary disease. MCA sensitivity and specificity were 87.5% and 76.9%, respectively, and the positive predictive value 82.4%. 10 patients had elevated MCA and no evidence of disease (NED) during their follow-up, of whom 4 finally developed overt metastases. The 4 had a mean (S.D.) MCA value of 46.48 (18.26) U/ml during the lead time, versus 18.76 (2.69) U/ml in the other 6, who are still at high risk for developing overt metastases. Raised levels of MCA in patients with NED create a dilemma of "treat" versus "wait and see". Early treatment of patients with serially uprising MCA levels should be evaluated in a prospective randomised study to assess its ability to prevent or delay the development of overt metastatic disease and influence survival.

Inhibition by ascorbic acid of apoptosis induced by oxidative stress in HL-60 myeloid leukemia cells.

The human myeloid leukemia cell line HL-60 transports the oxidized form of ascorbic acid, dehydroascorbic acid (DHA), and accumulates reduced ascorbic acid. We studied the effect of ascorbic acid loading on apoptosis induced by serum- and glucose-free culture and by oxidative stress induced by H2O2. Uptake accumulation studies indicated that incubation of HL-60 cells with DHA resulted in the accumulation of intracellular ascorbic acid which decreased with time when cells were incubated in DHA-free medium. Exposure of HL-60 cells to increasing concentrations of H2O2 resulted in dose-dependent intracellular accumulation of peroxides, as determined by the use of the oxidation-sensitive fluorescent probe 2',7'-dichlorofluorescin-diacetate (DCFH-DA), which was accompanied by a decrease in intracellular ascorbic acid and an increase in apoptosis. A dramatic decrease in intracellular ascorbic acid was noted when preloaded HL-60 cells were exposed to 150 microM H2O2 (the concentration dropped from 5.2 +/- 0.6 mM to 3.6 +/- 0.1 mM in cells preincubated with 150 microM DHA). A dose-dependent protective effect of DHA was observed. Ascorbic acid loading also provided strong protection from apoptosis associated with serum- and glucose-free culture. Flow cytometry studies showed that exposure of HL-60 cells to 150 microM H2O2 resulted in decreased Bcl-2 expression that was associated with enhanced apoptosis (up to 33.6 +/- 2.6%). No significant variation of Bcl-2 expression was measured following exposure of HL-60 cells, loaded with ascorbic acid, to 150 microM H2O2 and only a slight increase (up to 10.1 +/- 3.1%) in apoptosis. These findings indicate that ascorbic acid can inhibit apoptosis induced by oxidative stress in HL-60 cells.

Ascorbic acid inhibits apoptosis induced by X irradiation in HL60 myeloid leukemia cells.

Exposure of cells to ionizing radiation can cause apoptosis. Since antioxidants have been shown to protect against radiation-induced apoptosis, in this study we have evaluated the putative protective effect of ascorbate against radiation-induced apoptosis as well as the production of peroxides in the cells. HL60 cells transport the oxidized form of ascorbic acid, dehydroascorbic acid (DHA), and accumulate reduced ascorbate. Exposure of the cells to 5-40 Gy X radiation resulted in induction of apoptosis. Preincubation of the cells with DHA reduced the level of apoptosis after exposure to 5-20 Gy. Exposure of the cells to 5 or 20 Gy X radiation did not affect the intracellular concentration of peroxides, while phorbol myristate acetate (PMA), which is known to induce production of H(2)O(2) in cells (and served as a control), resulted in an increase in peroxides and a decrease in intracellular ascorbate. Irradiation of the cells with 1-3 Gy resulted in up-regulation of expression of BCL2 without affecting the level of apoptosis. At higher doses of radiation, enhanced BCL2 expression did not prevent radiation-induced apoptosis. Loading of the cells with ascorbate prior to their exposure to 1-3 Gy X radiation did not affect the enhanced BCL2 expression observed in the irradiated cells. At higher doses of radiation, ascorbate decreased apoptosis and restored the level of BCL2 in the cells. Exposure of the cells to 3-20 Gy X radiation enhanced the cell surface expression of TNFRSF6 (formerly known as Fas/APO-1) antigen and enhanced anti-TNFRSF6 antibody-induced apoptosis of the cells. Ascorbate loading did not affect expression of TNFRSF6 and did not overcome the anti-TNFRSF6 antibody-induced apoptosis. In conclusion, our data demonstrate that exposure of HL60 cells to radiation enhanced BCL2 and TNFRSF6 expression. Ascorbate did not affect BCL2 or TNFRSF6 expression. We therefore conclude that it protects HL60 cells against radiation-induced apoptosis, although the mechanisms of protection must still be elucidated.